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    <title>Styling feature with CanvasGradient or CanvasPattern</title>
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          <h4 id="title">Styling feature with CanvasGradient or CanvasPattern</h4>
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          <p id="shortdesc">Example showing the countries vector layer styled with patterns and gradients.</p>
          <div id="docs"><p>First this example creates a reusable <a href="https://developer.mozilla.org/en-US/docs/Web/API/CanvasPattern"><code>CanvasPattern</code></a> and a <a href="https://developer.mozilla.org/en/docs/Web/API/CanvasGradient"><code>CanvasGradient</code></a>. The countries are loaded from a GeoJSON file. A style function determines for each country whether to use a fill with the pregenerated CanvasGradient (rainbow colors) or a CanvasPattern (repeating stacked circles).</p>
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          <div id="api-links">Related API documentation: <ul class="inline"><li><a href="../apidoc/ol.Map.html" title="API documentation for ol.Map">ol.Map</a></li>,<li><a href="../apidoc/ol.View.html" title="API documentation for ol.View">ol.View</a></li>,<li><a href="../apidoc/ol.extent.html" title="API documentation for ol.extent">ol.extent</a></li>,<li><a href="../apidoc/ol.format.GeoJSON.html" title="API documentation for ol.format.GeoJSON">ol.format.GeoJSON</a></li>,<li><a href="../apidoc/ol.has.html" title="API documentation for ol.has">ol.has</a></li>,<li><a href="../apidoc/ol.layer.Vector.html" title="API documentation for ol.layer.Vector">ol.layer.Vector</a></li>,<li><a href="../apidoc/ol.proj.html" title="API documentation for ol.proj">ol.proj</a></li>,<li><a href="../apidoc/ol.source.Vector.html" title="API documentation for ol.source.Vector">ol.source.Vector</a></li>,<li><a href="../apidoc/ol.style.Fill.html" title="API documentation for ol.style.Fill">ol.style.Fill</a></li>,<li><a href="../apidoc/ol.style.Stroke.html" title="API documentation for ol.style.Stroke">ol.style.Stroke</a></li>,<li><a href="../apidoc/ol.style.Style.html" title="API documentation for ol.style.Style">ol.style.Style</a></li></ul></div>
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        <form method="POST" id="jsfiddle-form" target="_blank" action="https://jsfiddle.net/api/post/library/pure/">
          <textarea class="hidden" name="js">var canvas &#x3D; document.createElement(&#x27;canvas&#x27;);
var context &#x3D; canvas.getContext(&#x27;2d&#x27;);

// Gradient and pattern are in canvas pixel space, so we adjust for the
// renderer&#x27;s pixel ratio
var pixelRatio &#x3D; ol.has.DEVICE_PIXEL_RATIO;

// Generate a rainbow gradient
function gradient(feature, resolution) {
  var extent &#x3D; feature.getGeometry().getExtent();
  // Gradient starts on the left edge of each feature, and ends on the right.
  // Coordinate origin is the top-left corner of the extent of the geometry, so
  // we just divide the geometry&#x27;s extent width by resolution and multiply with
  // pixelRatio to match the renderer&#x27;s pixel coordinate system.
  var grad &#x3D; context.createLinearGradient(0, 0,
      ol.extent.getWidth(extent) / resolution * pixelRatio, 0);
  grad.addColorStop(0, &#x27;red&#x27;);
  grad.addColorStop(1 / 6, &#x27;orange&#x27;);
  grad.addColorStop(2 / 6, &#x27;yellow&#x27;);
  grad.addColorStop(3 / 6, &#x27;green&#x27;);
  grad.addColorStop(4 / 6, &#x27;aqua&#x27;);
  grad.addColorStop(5 / 6, &#x27;blue&#x27;);
  grad.addColorStop(1, &#x27;purple&#x27;);
  return grad;
}

// Generate a canvasPattern with two circles on white background
var pattern &#x3D; (function() {
  canvas.width &#x3D; 11 * pixelRatio;
  canvas.height &#x3D; 11 * pixelRatio;
  // white background
  context.fillStyle &#x3D; &#x27;white&#x27;;
  context.fillRect(0, 0, canvas.width, canvas.height);
  // outer circle
  context.fillStyle &#x3D; &#x27;rgba(102, 0, 102, 0.5)&#x27;;
  context.beginPath();
  context.arc(5 * pixelRatio, 5 * pixelRatio, 4 * pixelRatio, 0, 2 * Math.PI);
  context.fill();
  // inner circle
  context.fillStyle &#x3D; &#x27;rgb(55, 0, 170)&#x27;;
  context.beginPath();
  context.arc(5 * pixelRatio, 5 * pixelRatio, 2 * pixelRatio, 0, 2 * Math.PI);
  context.fill();
  return context.createPattern(canvas, &#x27;repeat&#x27;);
}());

// Generate style for gradient or pattern fill
var fill &#x3D; new ol.style.Fill();
var style &#x3D; new ol.style.Style({
  fill: fill,
  stroke: new ol.style.Stroke({
    color: &#x27;#333&#x27;,
    width: 2
  })
});

/**
 * The styling function for the vector layer, will return an array of styles
 * which either contains the aboove gradient or pattern.
 *
 * @param {ol.Feature} feature The feature to style.
 * @param {number} resolution Resolution.
 * @return {ol.style.Style} The style to use for the feature.
 */
var getStackedStyle &#x3D; function(feature, resolution) {
  var id &#x3D; feature.getId();
  fill.setColor(id &gt; &#x27;J&#x27; ? gradient(feature, resolution) : pattern);
  return style;
};

// Create a vector layer that makes use of the style function above…
var vectorLayer &#x3D; new ol.layer.Vector({
  source: new ol.source.Vector({
    url: &#x27;https://openlayers.org/en/v3.20.0/examples/data/geojson/countries.geojson&#x27;,
    format: new ol.format.GeoJSON()
  }),
  style: getStackedStyle
});

// … finally create a map with that layer.
var map &#x3D; new ol.Map({
  layers: [
    vectorLayer
  ],
  target: &#x27;map&#x27;,
  view: new ol.View({
    center: ol.proj.fromLonLat([7, 52]),
    zoom: 3
  })
});
</textarea>
          <textarea class="hidden" name="css">#map {
  /* Image craeted by tatyana, from https://sftextures.com/2014/10/22/blue-sky-with-blurred-white-clouds-seamless-textures/ */
  background-image: url(&#x3D;&#x3D;);
  background-repeat: repeat;
}
</textarea>
          <textarea class="hidden" name="html">&lt;div id&#x3D;&quot;map&quot; class&#x3D;&quot;map&quot;&gt;&lt;/div&gt;
</textarea>
          <input type="hidden" name="wrap" value="l">
          <input type="hidden" name="resources" value="https://openlayers.org/en/v3.20.0/css/ol.css,https://openlayers.org/en/v3.20.0/build/ol.js">
        </form>
        <pre><code id="example-source" class="language-markup">&lt;!DOCTYPE html&gt;
&lt;html&gt;
  &lt;head&gt;
    &lt;title&gt;Styling feature with CanvasGradient or CanvasPattern&lt;/title&gt;
    &lt;link rel="stylesheet" href="https://openlayers.org/en/v3.20.0/css/ol.css" type="text/css"&gt;
    &lt;!-- The line below is only needed for old environments like Internet Explorer and Android 4.x --&gt;
    &lt;script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"&gt;&lt;/script&gt;
    &lt;script src="https://openlayers.org/en/v3.20.0/build/ol.js"&gt;&lt;/script&gt;
    &lt;style&gt;
      #map {
        /* Image craeted by tatyana, from https://sftextures.com/2014/10/22/blue-sky-with-blurred-white-clouds-seamless-textures/ */
        background-image: url(&#x3D;&#x3D;);
        background-repeat: repeat;
      }
    &lt;/style&gt;
  &lt;/head&gt;
  &lt;body&gt;
    &lt;div id&#x3D;&quot;map&quot; class&#x3D;&quot;map&quot;&gt;&lt;/div&gt;
    &lt;script&gt;
      var canvas &#x3D; document.createElement(&#x27;canvas&#x27;);
      var context &#x3D; canvas.getContext(&#x27;2d&#x27;);

      // Gradient and pattern are in canvas pixel space, so we adjust for the
      // renderer&#x27;s pixel ratio
      var pixelRatio &#x3D; ol.has.DEVICE_PIXEL_RATIO;

      // Generate a rainbow gradient
      function gradient(feature, resolution) {
        var extent &#x3D; feature.getGeometry().getExtent();
        // Gradient starts on the left edge of each feature, and ends on the right.
        // Coordinate origin is the top-left corner of the extent of the geometry, so
        // we just divide the geometry&#x27;s extent width by resolution and multiply with
        // pixelRatio to match the renderer&#x27;s pixel coordinate system.
        var grad &#x3D; context.createLinearGradient(0, 0,
            ol.extent.getWidth(extent) / resolution * pixelRatio, 0);
        grad.addColorStop(0, &#x27;red&#x27;);
        grad.addColorStop(1 / 6, &#x27;orange&#x27;);
        grad.addColorStop(2 / 6, &#x27;yellow&#x27;);
        grad.addColorStop(3 / 6, &#x27;green&#x27;);
        grad.addColorStop(4 / 6, &#x27;aqua&#x27;);
        grad.addColorStop(5 / 6, &#x27;blue&#x27;);
        grad.addColorStop(1, &#x27;purple&#x27;);
        return grad;
      }

      // Generate a canvasPattern with two circles on white background
      var pattern &#x3D; (function() {
        canvas.width &#x3D; 11 * pixelRatio;
        canvas.height &#x3D; 11 * pixelRatio;
        // white background
        context.fillStyle &#x3D; &#x27;white&#x27;;
        context.fillRect(0, 0, canvas.width, canvas.height);
        // outer circle
        context.fillStyle &#x3D; &#x27;rgba(102, 0, 102, 0.5)&#x27;;
        context.beginPath();
        context.arc(5 * pixelRatio, 5 * pixelRatio, 4 * pixelRatio, 0, 2 * Math.PI);
        context.fill();
        // inner circle
        context.fillStyle &#x3D; &#x27;rgb(55, 0, 170)&#x27;;
        context.beginPath();
        context.arc(5 * pixelRatio, 5 * pixelRatio, 2 * pixelRatio, 0, 2 * Math.PI);
        context.fill();
        return context.createPattern(canvas, &#x27;repeat&#x27;);
      }());

      // Generate style for gradient or pattern fill
      var fill &#x3D; new ol.style.Fill();
      var style &#x3D; new ol.style.Style({
        fill: fill,
        stroke: new ol.style.Stroke({
          color: &#x27;#333&#x27;,
          width: 2
        })
      });

      /**
       * The styling function for the vector layer, will return an array of styles
       * which either contains the aboove gradient or pattern.
       *
       * @param {ol.Feature} feature The feature to style.
       * @param {number} resolution Resolution.
       * @return {ol.style.Style} The style to use for the feature.
       */
      var getStackedStyle &#x3D; function(feature, resolution) {
        var id &#x3D; feature.getId();
        fill.setColor(id &gt; &#x27;J&#x27; ? gradient(feature, resolution) : pattern);
        return style;
      };

      // Create a vector layer that makes use of the style function above…
      var vectorLayer &#x3D; new ol.layer.Vector({
        source: new ol.source.Vector({
          url: &#x27;https://openlayers.org/en/v3.20.0/examples/data/geojson/countries.geojson&#x27;,
          format: new ol.format.GeoJSON()
        }),
        style: getStackedStyle
      });

      // … finally create a map with that layer.
      var map &#x3D; new ol.Map({
        layers: [
          vectorLayer
        ],
        target: &#x27;map&#x27;,
        view: new ol.View({
          center: ol.proj.fromLonLat([7, 52]),
          zoom: 3
        })
      });
    &lt;/script&gt;
  &lt;/body&gt;
&lt;/html&gt;</code></pre>
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